Could Carly Fiorina's campaign suffer if she makes the next Republican debate?

Carly Fiorina looks set to appear on the main stage at the second Republican presidential debate, which will take place in Simi Valley, Nevada on 16 September.

This may be the best thing that could happen to the presidential campaign of the former Hewlett-Packard chief executive. It may also be the worst.

On Tuesday evening, CNN announced that it was changing its criteria for the main debate to include candidates who were in the top 10 in national polling either from 16 July to 10 September 10 or between 7 August and 10 September. Previously, only the first group would have qualified.

This will benefit Fiorina, as the second time period includes only polls taken after her strong performance in the first second-tier debate, in Cleveland on 6 August.

Fiorina, the only woman in the 17-strong GOP field, has surged in national polls since then, as well as in polls concerning two crucial early voting states, Iowa and New Hampshire.

The expected result of CNN’s new rules, then, is that Fiorina will appear on stage in the main debate, with the 10 candidates who participated last time. This will serve to validate her long-shot campaign and give her exposure to a national audience.

It may also halt her momentum.

Fiorina’s success in the first debate was in part due to the fact that she was one of only seven candidates in a slightly more relaxed and less confrontational setting which, of course, did not feature Donald Trump.

She had plenty of time to make her case. In an hour-long debate, she was able to talk for seven minutes. In the main, two-hour event, only Jeb Bush and Trump spoke for longer.

It will be far more difficult for Fiorina to give another breakout performance. Instead, her absence will give other candidates the opportunity to repeat her success in the second tier.

With Fiorina gone and former Virginia governor Jim Gilmore excluded, there will now only be five candidates in the early debate. It is likely one of them will steal the show.

It is still preferable, though, for candidates to be in the main debate. After all, the first debate attracted 24 million viewers and set ratings records. Just being on stage was invaluable.

But sometimes, to paraphrase Milton, it may be better to reign in happy hour than serve in prime time.